Porcelain enamel is subject to corrosion and dissolution by hot water. This can cause difficulties in applications such as hot water heaters. In a water heater, once the porcelain enamel coating protecting a metal substrate is dissolved through to the substrate, then the substrate corrodes rapidly and is perforated through. At this point the water heater must be replaced.
Attempts to improve the corrosion resistance of porcelain enamel have resulted in the use of various mill additions. However, mill additions that improve corrosion resistance tend to result in porcelain enamels that are subject to fish scaling or crazing.
Therefore, it would be desirable to have an improved porcelain enamel coating which is not only highly water-resistant, but also resists crazing or cracking.